1. Field of the Invention
The present invention relates to a data converter that converts image data into image data in a data format suitable for an output device, and a data conversion program storage medium that stores a data conversion program that makes a computer to perform such image data conversion.
2. Description of the Related Art
In recent years, computerization of printing technology has been advanced, and desktop publishing (DTP) for editing pages of prints on a computer has become popular. Typical kinds of DTP software used by operators to edit pages use page description languages (PDL), such as post script (PS) and portable document format (PDF), to describe pages. The DTP software produces image data that represents an image of a page with the positions of the elements, such as characters and photographs, fixed. The image data produced by the DTP software contains element data sections that represent the individual elements in the page and descriptions of the positions of the elements arranged in the page.
In production of plural pieces of direct mail or the like addressed to different destinations, for example, variable printing is often utilized. In the variable printing, image data is edited for output in such a manner that plural pages are described by handling plural pieces of direct mail as one printing group, an element data section that describes a master element, such as a stamp mark and an illustration, which commonly appears in plural pages, is shared among the plural pages, and an element data section that describes a variable element, such as an address and personalized information, which differs among pages, is replaced with an appropriate one for each page. In recent years, a page description language (PDL) referred to as a personal print markup language (PPML), which enables efficient edit of pages in variable printing, has become widely known (see Japanese Patent Laid-Open No. 2003-316549). Such a PPML permits previous declaration that the master element is shared among plural pages. When describing pages to be variable-printed in the PS or PDF, any master element commonly appearing in plural pages has to be described for each page. However, if the PPML is used, any master element has to be described just one time when the master element appears for the first time, and the master element once described can be utilized again when the same master element appears in another page. Therefore, the PPML can allow simple description of an easily legible page and reduce the total amount of image data.
If such variable printing is performed by a conventional printing machine that transfers ink applied to a printing plate onto a sheet of paper, many printing plates prepared for each address or personalized information are wasted. Therefore, instead of such a printing machine, there is used a printer-type output device that directly outputs characters or images onto a sheet of paper based on image data. However, such an output device, such as a printer, cannot output image data described in the PS, PDF, PPML or the like that is produced by DTP software as it is. Therefore, there have been known a data converter that converts image data into image data in a data format suitable for the output device through a raster image processor (RIP) processing that converts an element described in the PS into a raster image, an assembly processing that arranges the raster image converted from the element in a page, and the like, and a data conversion program that makes a computer perform such conversion (see National Publication of International Patent Application No. 2001-518417 (FIG. 2), for example).
However, many output devices for producing prints that replace printing machines are of a type that represents numerous colors by overlapping plural basic colors (for example, four colors of cyan (C), magenta (M), yellow (Y) and black (K)) as with the printing machines. In general, such output devices require, as image data, plural pieces of plate data that represent plural color-separated images, which result from separation of an image into images of the basic colors. Thus, the data converter is required to produce the plural pieces of plate data, and in the variable printing, such plural pieces of plate data have to be successively produced at a rate beyond the output capability of the output device. However, there are problems that the processing load is too heavy for the conventional data converter and the production of plate data is too slow for the output device having a high output capability.